"Giovanni" <blastingproton@gmail.com> wrote
news:1178536761.366580.89000@p77g2000hsh.googlegro ups.com...

> anyway, do you know if delta could be too large to stay in SECOND TYPE
> and so reset itself to 0?

You mean if there migth happen an error (overflow)?

I just did the following experiment:

mysql> DROP TABLE statistiche;
Query OK, 0 rows affected (0.03 sec)

mysql>
mysql> CREATE TABLE statistiche
-> (
-> risoluzione DATETIME,
-> inizio DATETIME
-> )
-> ENGINE = MyISAM;
Query OK, 0 rows affected (0.15 sec)

[adding your 10 rows into table]

mysql> INSERT INTO statistiche VALUES ('2007-05-04 23:43:53', '1980-05-04
00:43:53');
Query OK, 1 row affected (0.01 sec)

mysql> INSERT INTO statistiche VALUES ('2007-05-04 23:43:53', '0001-05-04
00:43:53');
Query OK, 1 row affected (0.00 sec)

mysql> SELECT risoluzione, inizio, timediff(risoluzione,inizio) AS delta
-> FROM statistiche
-> WHERE risoluzione IS NOT NULL
-> ORDER BY TIME_TO_SEC(delta) ASC;
+---------------------+---------------------+-----------+
| risoluzione | inizio | delta |
+---------------------+---------------------+-----------+
| 2007-04-29 15:16:55 | 2007-04-29 15:15:55 | 00:01:00 |
| 2007-05-02 23:25:04 | 2007-05-02 23:23:57 | 00:01:07 |
| 2007-05-05 20:28:21 | 2007-05-05 20:26:12 | 00:02:09 |
| 2007-05-05 10:21:08 | 2007-05-05 10:18:47 | 00:02:21 |
| 2007-04-30 16:52:50 | 2007-04-30 16:45:37 | 00:07:13 |
| 2007-05-05 14:23:42 | 2007-05-05 13:40:07 | 00:43:35 |
| 2007-04-29 23:58:17 | 2007-04-29 22:26:36 | 01:31:41 |
| 2007-05-04 12:07:43 | 2007-05-01 08:58:28 | 75:09:15 |
| 2007-05-04 23:43:53 | 2007-05-01 14:11:14 | 81:32:39 |
| 2007-05-05 16:35:21 | 2007-04-30 21:10:16 | 115:25:05 |
| 2007-05-04 23:43:53 | 1980-05-04 00:43:53 | 838:59:59 |
| 2007-05-04 23:43:53 | 0001-05-04 00:43:53 | 838:59:59 |
+---------------------+---------------------+-----------+
12 rows in set, 4 warnings (0.00 sec)

So even the difference of over 2000 years did not cause any error. Looks
like you are on the save side when using this query.

But you might have noted that the TIMEDIFF function shows only values up to
838:59:59 which represent a time difference of almost 34 days and 23 hours.
Which is a much smaller time difference then the 2000 years I used to test
the query.
--
Matthias Wirtz - Karlsruhe, DE